A new pitfall in potassium testing: A case series of false elevation of hemolysis index in the presence of monoclonal protein

Hemolysis is the most common preanalytical interfering factor and a major source of error in clinical biochemistry analysis. Modern laboratories routinely assess hemolysis in conjunction with a laboratory information system algorithm that automatically adds a comment or rejects test values when appropriate. The hemolysis index has largely replaced visual inspection for assessing specimen quality prior to clinical chemistry testing. However, visual inspection of samples after centrifugation can provide valuable information about preanalytical interferences. In this report, we present a case series of inaccurate assessment of hemolysis index associated with the presence of monoclonal protein leading to inappropriate suppression of potassium results by the laboratory information system algorithm. These samples were originally identified as strongly hemolysed by the hemolysis index on the Atellica CH930 automated chemistry analyser. However, visual inspection revealed clear plasma, suggesting that the elevated hemolysis index was not due to hemolysis. This report highlights the need to be aware of potential monoclonal protein interference with the hemolysis index for better interpretation of results, and proposes three warning signs to detect this type of anomaly.